The long-term objectives of the proposed studies are to understand the role that early environment plays in the development of asymmetries in manual gestures and facial expressions and their relationship to different structures of the brain. In the proposed research, behavioral studies on functional asymmetries in hand use for gestural communication and facial expressions used with referential vocalizations will be correlated with neuroanatomical asymmetries as assessed by magnetic resonance imaging (MRI). Specifically, whether hand use for gestures represents a unique functional asymmetry or whether it reflects a general asymmetry for all motor functions will be assessed by comparing handedness indices for gestures compared to motor tasks with similar situational demands. In another series of experiments, the influence of vocal communication on the expression of hand use for referential gestures will be assessed to determine whether the vocal signals enhance or inhibit the magnitude of asymmetries in communicative behavior. In a third set of experiments, asymmetries in facial expressions that made by bonobos that have a referential function will be compared to asymmetries in facial expressions that are not accompanied by the use of a referential vocalization. Finally, laterality in gestural communication and facial expressions will be correlated with asymmetries in the brain from specific regions of interest including the planum temporale, motor/hand area of the precentral gyrus, cingulate gyrus and basal ganglia. In addition, asymmetries in cortical connectivity using diffusion tensor imaging (DTI) will be assessed and compared between hemispheres. Of specific interest in all analyses will be the comparison of ape subjects that have been reared by humans and exposed to human language compared to those reared by conspecifics. This comparison will allow for determination of how human environments and communication systems may alter the development of communicative behavior and the cerebral organization of bonobos and chimpanzees. Overall, the proposed research will lead a better understanding of factors which influence the development of the central nervous system and its behavioral and communicative correlates.